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Wednesday, September 5, 2012

Why the fairer sex is also the tougher one: Women have superior systems to men

For centuries they’ve been labeled as the weaker sex.

But when it comes to the battlefield of illness and infections, women are far more robust than their male counterparts.

For it appears Mother Nature has given women a superior immune system, enabling them to fend off germs that leave men struggling to cope.

Feeling fit: Women may be called the fairer sex but in fact they have much more robust immune systems

According to a study, the fairer sex is genetically programmed to better resist infections and cancer, and also has a back-up system for fighting disease.

The discovery also suggests that males who regularly complain of ‘man-flu’ may not be exaggerating after all.

The secret to women’s stronger immunity lies in a key biological difference between the sexes. Women have an extra copy of the female X-chromosome, while men have only one and a much smaller Y-chromosome.

This means women have greater access to molecules called microRNAs, which are encoded on the X-chromosome. These tiny strains of ribonucleic acid are regarded as major regulators of the immune system.

Dr Claude Libert, from Ghent University in Belgium, led the research which drew up a detailed map of all the microRNAs in X-chromosomes found to have a role in immune functions and cancer.

He said: ‘Statistics show that in humans, as with other mammals, females live longer than males and are more able to fight off shock episodes from sepsis, infection or trauma.

‘We believe this is due to the X-chromosome, which in humans contains ten per cent of all microRNAs detected so far in the genetic code.’ Several of these are thought to have ‘important functions in immunity and cancer’, he said.

Dr Eleanor Fish, professor of women’s health and immunobiology at the University of Toronto, said of the findings in the BioEssays journal: ‘The advantages of having two X-chromosomes as opposed to an X- and a Y-chromosome are huge.

‘MicroRNAs are very important for regulating proteins that would influence cell growth and cancer, and the immune response.

‘They can suppress proteins that promote cancer and boost proteins that do the opposite.’

If women develop a mutation on a gene linked to the immune system on the X-chromosome, they have a backup copy. But men do not.

From a biological point of view, she added, the difference has probably evolved because women are more likely to ensure the survival of a species.

They need to be able to resist infection when pregnant and when nurturing the child. ‘You don’t need many men to keep the human race going but you need females,’ she said.

However, there is a downside to a woman’s super immunity, said Dr Fish: ‘It favors resistance to infection with a more robust immune response but once you have got infection then it can result in a more severe inflammatory response.

‘This means women are more likely to develop autoimmune diseases and they may suffer flu more badly than men.’